Haulage system for excavated material



M r h 1 1963 E. R. BORCHERDT HAULAGE SYSTEM FOR EXCAVATED MATERIAL Filed Nov. 9, 1959 INVENTOR EDWARD R. BORCHERDT BY r[;/

ATTORNEYS United States Patent 3 080 982 HAULAGE SYSTEM non FJXCAVATED MATERIAL Edward R. Borcherdt, Butte, Mont, assignor to The Anaconda Company, a corporation of Montana Filed Nov. 9, 1959, Ser. No. 851,741 8 Claims. (Cl. 2141) This invention relates to means for hauling excavated material and, more particularly, to a haulage system for an open pit mining or stripping operation or the like which includes a relatively steep trolley roadway slop ing upwardly out of the pit and a plurality of electric trolley trucks which can ascend the roadway at relatively high speed with heavy loads and which are equipped with auxiliary motor-generator units for low-speed operation independent of the trolley.

Excavated material is conventionally hauled from an open pit mine over an inclined roadway, often spiralling upwardly from the bottom of the pit, by means of a number of diesel trucks of 30 to 50 tons maximum capacity which travel up and down the roadway from a loading area on the floor of the pit to a dumping area outside the pit. To insure that the trucks can operate even under bad weather conditions, the slope of such a roadway does not normally exceed about a 7 percent grade. Typical heavy-duty diesel trucks of up to approximately 600 horsepower can ascend roadways of this type at speeds of about 3 or 4 mph. maximum, though at the high altitudes where many open pit mines are located their output horsepower may be as much as onethird their sea-level rating.

It is the primary purpose of the present invention to provide a' considerably improved haulage system for transporting excavated material from open pit mines and the likewhich greatly reduces the personnel, power costs, and time required to remove a given amount of excavated material. For transporting the excavated material from'the bottom of the pit to a dumping area outside of the pit, the invention provides a particularly steep roadway having a grade of 15 percent or more, so that its length for a predetermined rise may be exceptionally short. In fact, it is contemplated that in many cases such a roadway may be directed upwardly out of the mine pit in a straight line without spiralling up in the conventional manner. The invention also proposes to use heavy trucks of as much as 70 to 100 tons capacity whic can ascend the roadway when loaded at speeds of up to about 15 mph, notwithstanding the steep grade. It is a further object that these trucks be substantially unaffected by high-altitude operation.

These and other advantages are fully achieved in the new haulage system for transporting excavated material from an open pit mine. The new system includes a 3,986,982 Patented Mar. 12, 1963 of the trolley wires. By these means, the truck can be driven at low speed between the loading area and lower terminus and the dumping area and upper terminus of the roadway and at high speed on the roadway itself.

In one form of the invention, guiding means are included for automatically steering the truck as it travels over the roadway. Thus, the truck can be driven at low speed by an operator between the loading area and lower terminus and the dumping area and upper terminus of the roadway and at high speed without an operator on the roadway itself. Also, the truck may be powered by a plurality of motors mounted in a respective plurality of truck wheels. Such motors may provide electro-dynamic braking means for braking the truck during its downward travel on the roadway. Resistance means on the truck may be included for dissipating elec trical energy generated by these braking means.

One of the most important characteristics of this new haulage system is that the electric trucks employed are supplied with a great amount of power when they most need it, that is, as they ascend the roadway out of the pit while carrying a full load. This means that the trucks can haul greater loads at faster speeds up steeper grades than ever before. At the same time, they supply themselves with suflicient power from their auxiliary generators to operate independently of the trolley at the .lower loading area and the upper dumping area. Thus,

loading area on the floor of the pit and a dumping area outside of the pit. An inclined roadway slopes upwardly from a lower terminus on the floor of the pit removed from the loading area to an upper terminus outside of the pit removed from the dumping area. A plurality of towers are spaced alongside this roadway from the lower to the upper terminus thereof and trolley wires are suspended from the towers above the roadway throughout substantially its entire length. A source of electrical power is provided for delivering current to these trolley wires.

For carrying the excavated material, at least one electrioally driven truck is included. Trolley following means are mounted on the truck for collecting sufiicient power from the trolley wires to permit high-speed operation of vthe truck on the roadway. An electric generator powered by an internal combustion engine is mounted in the truck for delivering suflicient power to the electric motors to permit low-speed operation of the truck independently the trolley wires and towers are confined to the roadway where they do not interfere with the operation of the shovels and other excavating equipment in the loading area. In this regard, a portable form of trolley tower is provided to permit an especially flexible arrangement of the new haulage system. Also, as a result of the above-mentioned guiding system, hostlers are required to drive the trucks only between the loading and dumping areas and the upper and lower ends of the roadway respectively, and not on the considerably longer incline of the roadway itself.

A preferred embodiment of the new haulage system is described below, wherein FIG. 1 is a schematic vertical section of an open pit mine equipped with the haulage system of the invention;

FIG. 2 is a perspective view of a base for the trolley towers which renders the towers portable; and

FIG. 3 is an enlarged elevation partly in sectionof an electric truck of the type described operating on the trolley cables and being steered by guiding means in the roadway.

In FIG. 1, an open pit mine 10 is shown which includes a floor 11 and walls 12, which may be in the usual bench form, being excavated progressively into or toward the deposit of ore being mined. (Quarries, strip mines, excavations for dams etc. are also typical of the type of operations where the new haulage system is useful.) Explosives are normally used to blast the material free and the resulting loose material is gathered up by shovels as shown at 3. The excavated material, whether it be ore or waste material or both, is then transported from the shovel 13, at what may be called a loading area 15, to a dumping area 1'7 outside of the mine pit 10.

According to the invention, the excavated material is hauled out of the pit It) over an inclined roadway l9 sloping a considerable distance upwardly from a lower terminus 20 on the floor 11 of the pit to an upper terminus 21 outside of the pit. This roadway 19 may have an upward grade of about 15 percent, and if the area covered by the pit 10 is great enough it may ascend in a straight line, as shownin FIG. 1. Preferably, the lower terminus 24) of the roadway 19 is removed from the loading area 15 on the pit floor 11 so that the roadway does not interfere with excavation operations. Similarly, the upper terminus 21 of the roadway 19 is often removed from the dumping area 17, particularly when it is a waste dump, because its periphery thus extends progressively farther out from the terminus 21 as it is filled with waste material.

In the form shown, the roadway 19 includes two adjacent parallel trafiic lanes 22 and 22 for use by descending and ascending trafic respectively. Each of the lanes 22 and 22 is surfaced with gravel and compacted by a roller. If prolonged heavy use of the roadway 19 is anticipated, a more permanent surface may be applied to the lanes 22 and 22', such as a surface of sanded asphalt. A plurality of towers 23 are spaced between the lines 22 and 22 of the roadway from the lower terminus 20 thereof to theupper terminus 21. Each of the towers 23 includes a superstructure 24 extending laterally outwardly over the respective lanes 22 and 22'.

In FIG. 2, a specially designed portable base is shown for supporting the individual towers 23. The base includes a large block 25 of concrete resting on parallel rails 26 and 26' which are secured to the underside of the block in any suitable manner. This permits the fork of a lift truck to be inserted beneath the base so that the base may be easily transported. Set into the upper face of the block 25 is a vertical open-ended socket pip-e 27 adapted to removably receive a primary upright member 28 of the trolley tower. et screws may be provided in the pipe 27 to lock the member 28 in place. Bases of this type may be arranged and rearranged at will along the roadway or adjacent the loading and dumping stations.

Suspended from the opposite ends of the superstructure 24 of the towers 215 are two pairs of trolley wires 29' and 29' which extend longitudinally above the center line of the respective lanes 22 and 22 throughout their entire length. At least one rectifier is located in a control station 31 adjacent the roadway 19, at the lower terminus 20 in the embodiment shown in FIG. 1, to which high-voltage alternating-current may be delivered from a power line. The rectifier converts this line current into direct-current which is delivered to the pairs of trolley Wires 29 and 29' by connectors 33 and 34 respectively. As much as 3000 amperes or more of direct current may be delivered to the pairs of trolley cables from the rectifier in this manner.

In this embodiment, a pair of signal-transmitting guiding cables 36 (only one of which is shown in the section of FIG. 1) is buried several inches beneath the respective lanes'22 and 22' of the roadway 19 centrally throughout their entire length. Energizing means are provided in the control station 31 for activating each of the guiding cables 36. This may be achieved by connecting the upper ends of the guiding cables 36' and impressing an A.-C. voltage across their lower ends so that an alternating magnetic flux field is created around the cables as throughout their entire length. The strength of the energizing means should be strong enough so that the signals transmitted by the cables 36 can be readily detected above the adjacent surface of the respective lanes 22 and 22' of the roadway, but controlled sur'liciently so that the signals transmitted by one cable cannot be detected closely above the other cable.

The actual hauling of the excavated material from the loading area 15 to the dumping area 17 is accomplished by means of a plurality of trucks 38, one of which is shown in detail in FIG. 3. According to the invention, each of the trucks 3% includes a load-carrying body por tion 40 having a capacity of as much as 100 tons of excavated material 41. The trucks 3% are equipped with widebase tubeless tires 42 of large diameter each mounted about what is known as an electric motor wheel 43. Such wheels 43 are direct-current series-wound electric motors which have an armature shaft geared to the rim of the tire 42. Thus, the driving motors of the trucks 38 are mounted directly in their wheels and no transmissions or axles are required. The horsepower rating of these electric motor wheels 43 may be in total as much as 1600 H.P. to ascend a 15 percent grade with a load of as much as tons of material. The United States patents to Le Tourncau Nos. 2,733,770 and 2,763,331, contain discussion of heavy duty trucks and electric motor wheels which may be appropriate in the practice of this invention.

When the trucks 38 descend the lane 22 of the roadway 19, the electric motor wheels 43 generate direct-current which is returned through the trolley wires 29 and 29' to other trucks 3S ascending the lane 22 of the roadway. By electro-dynamically braking the trucks 33 in this manner, the braking energy may be conserved in the electrical system. Also, it becomes unnecessary to incor porate large friction brakes in the trucks which are subject to wear, though small friction brakes must still be included for ordinary level braking. If there are no trucks ascending the lane 22 as the descending trucks are electro-dynamically braked, it is necessary that some means be included for dissipating the energy generated in the brakes. Hence, large resistance dissipators 44 (see FIG. 3) are provided to transmit this energy in the form of heat to the surrounding air. The subject of dynamic braking of this sort is treated, for example, in the aforementioned Le Tourneau Patent No. 2,733,770.

The invention provides two alternate means for energizing the electric wheel motors 43 of the trucks 38. First, for low-speed operation on relatively level ground, a direct-current generator powered by a diesel motor 45 is mounted on the truck. This diesel-driven generator is capable of delivering enough power to the electric motor wheels 43 to permit the trucks to travel independently of the trolley wires 29 and 29 on relatively level ground with full load at about 4 or 5 rn.p.h., particularly between the loading area 15 and lower terminus 20 and dumping area 17 and upper terminus 21. Second, for high-speed operation on the roadway 19, a pair of trolley poles 47 and 48 are pivotally mounted on each truck to follow the respective wires of one of the pairs of trolley wires 29 and 29'. Thus, the poles 47 and 43 include follower means 50 and 51 respectively at their outermost ends for engagement with the trolley wires. When not in use, the trolley poles 47 and 48 can be lowered and secured to the truck 33. When inuse, they deliver the high directcurrent from the trolley wires to the electric motor wheels 43 to permit the trucks 38 to ascend the roadway 19 at as much as 15 mph. while carrying a full load. A typical arrangement for alternate trolley or motor-generator operation is discussed in the United States patent to Potter, No. 2,600,320.

Also included in each of the trucks 38 is a conventional sensing means 53 which receives the signal transmitted by one of the guiding cables 36 in the lanes 22 and 22 of the roadway. The sensing means 53 should be of the type which determines whether it is directly over, to the left of, or to the right of the guiding cable 36 transmitting the signal. In response to this determination, a directionchanging device 54 in the truck 38 is actuated to steer the truck over the guiding cable 36 in its lane. Thus, when the trucks 38 are on the roadway 19, it is not necessary that a truck driver be in the cab to steer the truck out of the pit, since it is guided automatically by the above-described means. The United States patent to Paulus ct al. No. 2,317,400 is representative of a guidance system of this type for steering vehicles automatically.

Other guidance systems may be quite suitable, of course, for steering the trucks along the roadway without an operator. For example, the signal could be sent through the trolley wires themselves so that a buried cable would be unnecessary. Such a signal in the trolley wires might be an A.-C. voltage superimposed over the primary D.-C. voltage. Alternatively, a mechanical sensing device might be provided to note the angular displacement in a lateral direction of the trolley poles with respect to the trolley wires and to steer the truck accordroadway 19. reaches its top speed of about 25 mph, the electric motor iugly so that it is always guided immediately beneath its respective pair of trolley wires.

In'the operation of this new system for removing excavated material from an open pit mine, the trucks 3-8 are loaded successively with up to 100 tons of materal by the shovel 13, or other loading equipment, at the loading area 15 on the floor of the pit 10. A hostler then drives the loaded truck at about 4 or 5 mph. by means of its diesel-driven generator to the lower terminus 20 of the roadway 19. There he dismounts and connects the followers 50 and 51 of the trolley poles 47 and 48 to the pair of trolley Wires 29'. This energizes the elec- 'tric motor wheels 43 of the truck and it starts up the lane 22 of the roadway 19 at about 15 m.p.h. The signal transmitted by the guiding cable 36 under the lane 22 is picked up by the sensing means 53 which, in turn, activates the direction-changing device to steer the truck 38 over the guiding cable 36 along the center of the lane 22'. In this manner, the loaded truck proceeds without an'operator to the upper terminus 2 1 of the roadway 19 a where it comes to a stop when the followers 50 and 5-1 run off of the pair'of trolley wires 29'. A second hostler then mounts. the truck and drives it by means of its diesel-driven generator at about 4 or 5 mph. to the dumping area 17.

After unloading the truck, the second liostler drives the truck by its diesel-driven generator at 4 or 5 mph. back to the upper terminus 21 of the roadway 19. He

then connects the followers 50 and 51 of the trolley :poles 47 and 48 to the respective pair of cables 29 over the lane 22. The electric motor wheels 43 are thereby energized and the truck proceeds downwardly on the A-s the descending unloaded truck 38 wheels 43 generate a considerable amount of power which is delivered into the pair of trolley wires 29 for use by the other trucks 38 ascending the line 22 in the other direction or is absorbed in the dissipators 44. Upon reaching the lower terminus 20 of the roadway 19, the

fit at low speed hack to the loading area 15.

The exceptional efficiency of this system is the result unloaded truck comes to a halt and the operator drives of several unique advantages, not the least of which is that each of the trucks 38 can haul perhaps 20 to 30 percent more excavated material than can conventional diesel trucks. Combined with this is the fact that the trucks 38 can ascend the roadway out of the pit at a much faster speed than was ever possible with diesel trucks. Moreover, notwithstanding the increased speed and load of'the trucks 3-8, they are sufiiciently powerful to permit the roadway 19 to be inclined at the extraordinary grade of about 15 percent, which means that the length of the roadway 19 is much shorter for a given vertical rise. In addition, unlike diesel trucks, the trucks 38 are assured of operating on the roadway 19 up to their full potential horsepower rating regardless of the elevation above sea-level of the mine, since a rarefied atmosphere has little adverse effect on electric motors. Also, the saving in personnel costs made possible by the new system is obvious since truck drivers are not required to drive the trucks during the long ascent and descent on the roadway 19.

These advantages of the new haulage system are achieved, however, without in any way interfering with the normal excavating operations on the door of the mine pit or the dumping operations outside the pit. As noted above, the lower terminus 20 of the roadway 19 is removed from the loading area 15 so that the trolley wires 29 and Z9 and the towers 23 do not hinder the shovel 13 and other excavating equipment in their work. This is made possible by the incorporation in the trucks 38 of the auxiliary diesel-driven generator which permits the trucks to be operated, even when fully loaded, completely independently of the trolley cables. Also, it means that at the dumping area 17 outside of the pit, the trucks 38 can proceed directly to the desired dumping point not withstanding the fact that it may be removed from the upper terminus 21 of the roadway.

I claim:

1. A haulage system for transporting excavated material from an open pit mine or the like comprising a loading station on the fioor of said pit and a dumping station outside of said pit, an inclined roadway sloping upwardly from a lower terminus on the floor of said pit removed from said loading area to an upper terminus outside of said pit removed from. said dumping area, a plurality of towers spaced alongside said roadway from the lower to the upper terminus thereof, trolley Wires suspended from said towers above said roadway sub stantially throughout its length, a source of electrical power connected to said trolley wires for delivering electric current thereto, at leastone electrically driven truck adapted to carry excavated material, trolley following means'on said truck for collecting sufficient power from said trolley wires to permit high-speed operation of said truck on said roadway, and an electric generator powered by an internal combustion enginemounted in said truck for producing sufii-cient power to permit low-speed operation of said truck independently of said trolley, whereby said truck is driven at low speed between the loading area and lower terminus and the dumping area and upper terminus of the roadway and at high speed on the roadway itself.

2. A haulage system for transporting excavated material from an open pit mine or the like comprising a loading station on the floor of said pit and a dumping station outside of said pit, an inclined roadway sloping up,- wardly from a lower terminus on the floor of said pit removed from said loading area to an upper terminus outside of said pit removed from said dumping area, a

plurality of towers spaced alongside said roadway from the lower to the upper terminus thereof, trolley wires suspend-ed from said towers above said roadway substantially throughout its length, a source of electrical power connected to said trolley wires for delivering electric current thereto, at least one electrically driven truck adapted to carry excavated material, said truck being powered by a plurality of electric motors mounted in a respective plurality of the truck wheels, trolley following means on said truck for collecting sufiicient power from said trolley wires to permit high-speed operation of said truck on said roadway, and an electric generator powered by an internal combustion engine mounted in said truck for producing sufficient power to permit low-speed operation of said truck independently of said trolley, whereby said truck is driven at low speed be tween the loading area and lower terminus and the dumping area and upper terminus of the roadway and at high speed on the roadway itself.

3. A haulage system for transporting excavated material from an open pit mine or the like comprising a loading station on the floor of said pit and a dumping station outside of said pit, an inclined roadway sloping upwardly from alower terminus on the floor of said pit removed from said loading area to an upper terminus outside of said pit removed from said dumping area, a plurality of towers spaced alongside said roadway from the lower to the upper terminus thereof, trolley wires suspended from said towers above said roadway substantially throughout its length, a source of electrical power connected to said trolley wires for delivering electric current thereto, at least one electrically driven 'lcctingsufiicient power from said trolley wires to permit high-speed operation of said truck on said roadway, and an electric generator powered by an internal combustion engine mounted in said truck for producing sufficient power to permit low'speed operation of said truck independently of said trolley, whereby said truck is driven at low speed between the loading area and lower terminus and the dumping area and upper terminus of the roadway and at high speed on the roadway itself.

4. A haulage system for transporting excavated material from an open pit mine or the like comprising a loading station on the floor of said pit and a dumping station outside of said pit, an inclined roadway sloping upwardly from a lower terminus on the floor of said pit removed from said loading area to an upper terminus outside of said pit removed from said dumping area, a plurality of towers spaced alongside said roadway from the lower to the upper terminus thereof, trolley wires suspended from said towers above said roadway substantially throughout its length, a source of electrical power connected to said trolley wires for delivering electric current thereto, at least one electrically driven truck adapted to carry excavated material, trolley following means on said truck for collecting sufiicient power from said trolley Wires to permit high-speed operation of said truck on said roadway, guiding means for automatically steering said truck as'it travels over said roadway, and an electric generator powered by an internal combustion engine mounted in said truck for producing sufficient power to permitlow-speed operation of said truck independently of said trolley, whereby said truck is driven at low speed between the loading area and lower terminus and the dumping area and upper terminus of the roadway and at high speed without an operator on the roadway itself.

5. A haulage system for transporting excavated material from an open pit mine comprising a loading station on the floor of said pit and a dumping station outside of said pit, an inclined roadway sloping upwardly from a lower terminus on the floor of said pit removed from said loading area to an upper terminus outside of said pit removed from said dumping area, a plurality of towers spaced alongside said roadway from the lower to the upper terminus thereof, a pair of trolley wires suspended from said towers above said roadway throughout substantially its entire length, a source of electrical power for passing current through said trolley wires, signal-transmitting means extending continuously throughout the entire length of said roadway, energizing means for activating said signal-transmitting means, at least one truck of high load capacity adapted to carry excavated material, said truck being powered by a plurality of electric motors mounted in a respective plurality of the truck wheels, trolley following means on said truck for delivering suthcient power from said trolley wires to said electric motors to permit high-speed operation of said truck on said roadway, sensing means on said truck for receiving the transmitting means signal, directionchanging means in said truck responsive to said sensing means for steering said truck along said roadway, and an electric generator powered by an internal cornbustion engine mounted in said truck for delivering sufficient power to said electric motors to permit low-s ee operation of said trucl-z independent of said trolley wires, whereby said truck is driven at low speed by an operator between the loading area and lower terminus and the dumping area and upper terminus of the roadway and at high speed without an operator on the roadway itself.

6. A haulage system for transporting excavated material from an open pit mine comprising a loading station on the floor of said pit and a dumping station outside of said pit, an inclined double-lane roadway sloping a considerable distance upwardly from a lower terminus on the floor of said pit removed from said loading area to an upper terminus outside of said pit removed from said dumping area, one of said lanes being used for ascending trailic and the other for descending trafiic, a plurality of portable towers spaced alongside said roadway from the lower to the upper terminus thereof, two pairs of trolley wires suspended from said towers longitudinally above the respective lanes of said roadway throughout substantially their entire length, a source of electrical power for passing current through each pair of trolley wires, stationary signal-transmitting means extending substantially centrally throughout the length of each lane of said roadway, energizing means for activating said signal-transmitting means, a plurality of trucks of high load capacity adapted to carry excavated material, each of said trucks being powered by a plurality of electric motors mounted in a respective plurality of the truck wheels, trolley following means on each truck for delivering sufiicient power from said trolley wires to its electric motors to permit high-speed operation of said trucks on said roadway, sensing means on each of said trucks for receiving the transmitting means signal in one of said lanes, direction-changing means in each truck responsive to said sensing means for steering said trucks along the guiding means in one of said lanes, and an electric generator powered by a diesel motor mounted in each truck for delivering sufficient power to its electric motors to permit low-speed operation of said trucks independent of said trolley wires, whereby said trucks are driven at low speed by an operator between the loading area and lower terminus and the dumping area and upper terminus of the roadway and at high speed without an operator on said roadway.

7. A haulage system for transporting excavated material from an open pit mine comprising a loading station on the floor of said pit and a dumping station outside of said pit, an inclined double-lane roadway sloping a considerable distance upwardly from a lower terminus on the floor of said .pit removed from said loading area to an upper terminus outside of said pit removed from said dumping area, one of said lanes being used for ascending trafiic and the other for descending trafiic, a plurality of portable towers spaced alongside said roadway from the lower to the upper terminus thereof, two pairs of trolley wires suspended from said towers longitudinally above the respective lanes of said roadway throughout substantially their entire length, a source of electrical power for passing current through each pair of trolley wires, stationary signal-transmitting means extending substantially centrally throughout the entire length of each lane of said roadway, energizing means for activating said signal-transmitting means, a plurality of tracks of high load capacity adapted to carry excavated material, each of said trucks being powered by a plurality of electric motors mounted in the respective truck wheels, trolley following means on each truck for delivering sufiicient power from said trolley wires to its electric motors to permit high-speed operation of said trucks on said roadway, sensing means on each of said trucks for receiving the transmitting means signal in one of said lanes, direction-changing means in each truck responsive to said sensing means for steering said trucks along the guiding means in one of said lanes, electro-dynamic braking means provided by each electric motor in each of said trucks which brakes the trucks during their downward travel on the descending lane of said roadway, and an electric generator powered by a diesel motor mounted in each truck for delivering sufiicient power to its electric motors to permit low-speed operation of said trucks independent of said trolley cables, whereby said trucks are driven at low speed by an operator between the loading area and lower terminus and the dumping area and upper terminus of the roadway and at high speed able distance upwardly from a lower terminus on the floor of said pit removed from said loading area to an upper terminus outside of said pit removed from said dumping area, one of said lanes being used 'for ascending trailic and the other for descending trafiic, a plurality of portable towers spaced alongside said roadway from the lower to the upper terminus thereof, two pairs of trolley wires suspended from said towers longitudinally above the respective lanes of said roadway throughout substantially their entire length, a source of electrical power for passing direct current through each pair of trolley wires, a signaltransmitting guiding cable buried beneath each lane of said roadway extending substantially centrally throughout its entire length, energizing means for activating each guiding cable, a plurality of multi-wheel trucks of high load capacity adapted to carry excavated material, each of said trucks being powered by a plurality of direct current motors mounted in its respective truck wheels, a pair of pivotable trolley poles on each truck for following one of,

said pairs of trolley wires and delivering sufficient power from said trolley wires to said electric motors to permit high-speed operation of said trucks on said roadway, sensing means on each of said trucks for receiving the signal transmitted by the guiding cable buried in one of said lanes, direction-changing means in each truck responsive to said sensing means for steering said trucks along the guiding cable in one of said lanes, electro-dynarnic braking means provided by each electric motor in each of said trucks which brakes the trucks during their downward travel on the descending lane of said roadway and which is adapted to return electrical power to said trolley wires for use by the ascending trucks, resistance means on said truck for dissipating whatever electrical power generated by said braking means is not used by said ascending trucks, and a direct current generator powered by a diesel motor mounted in each truck for delivering sufiicient power to its electric motors to permit low-speed operation of said trucks independent of said trolley wires, whereby said trucks are driven at low speed by an operator between the loading area and lower terminus and the dumping area and upper terminus of the roadway and at high speed without an operator on the ascending and descending lanes of said roadway.

References Cited in the file of this patent UNITED STATES PATENTS 458,665 Seymour Sept. 1, 1891 714,157 Davis Nov. 25, 1902 729,826 Willard June, 2, 1903 873,703 Anderson Dec. 17, 1907 2,317,400 Paulus et al Apr. 27, 1943 2,339,291 Paulus Jan. 18, 1944 2,600,320 Potter June 10, 1952 2,733,770 .LeTourneau Feb. 7, 1955 2,742,099 Hagen Apr. 17,1956 2,763,331 LeTourn'eau Sept. 18, 1956 FOREIGN PATENTS 347,705 Great Britain Apr. 28, 1931 OTHER REFERENCES Mining Engineering, pages 405408, April 1959. 

1. A HAULAGE SYSTEM FOR TRANSPORTING EXCAVATED MATERIAL FROM AN OPEN PIT MINE OR THE LIKE COMPRISING A LOADING STATION ON THE FLOOR OF SAID PIT AND A DUMPING STATION OUTSIDE OF SAID PIT, AN INCLINED ROADWAY SLOPING UPWARDLY FROM A LOWER TERMINUS ON THE FLOOR OF SAID PIT REMOVED FROM SAID LOADING AREA TO AN UPPER TERMINUS OUTSIDE OF SAID PIT REMOVED FROM SAID DUMPING AREA, A PLURALITY OF TOWERS SPACED ALONGSIDE SAID ROADWAY FROM THE LOWER TO THE UPPER TERMINUS THEREOF, TROLLEY WIRES SUSPENDED FROM SAID TOWERS ABOVE SAID ROADWAY SUBSTANTIALLY THROUGHOUT ITS LENGTH, A SOURCE OF ELECTRICAL POWER CONNECTED TO SAID TROLLEY WIRES FOR DELIVERING ELECTRIC CURRENT THERETO, AT LEAST ONE ELECTRICALLY DRIVEN TRUCK ADAPTED TO CARRY EXCAVATED MATERIAL, TROLLEY FOLLOWING MEANS ON SAID TRUCK FOR COLLECTING SUFFICIENT POWER FROM SAID TROLLEY WIRES TO PERMIT HIGH-SPEED OPERATION OF SAID TRUCK ON SAID ROADWAY, AND AN ELECTRIC GENERATOR POWERED BY AN INTERNAL COMBUSTION ENGINE MOUNTED IN SAID TRUCK FOR PRODUCING SUFFICIENT POWER TO PERMIT LOW-SPEED OPERATION OF SAID TRUCK INDEPENDENTLY OF SAID TROLLEY, WHEREBY SAID TRUCK IS DRIVEN AT LOW SPEED BETWEEN THE LOADING AREA AND LOWER TERMINUS AND THE DUMPING AREA AND UPPER TERMINUS OF THE ROADWAY AND AT HIGH SPEED ON THE ROADWAY ITSELF. 